An artist's conception of Kepler-22b, a planet 600 light years away from Earth, and the first confirmed planet outside our solar system that could conceivably harbor life as we know it. NASA/Ames/JPL-Caltech

December 6, 2011

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Say hello to "Earth 2.0." NASA's planet-hunting Kepler spacecraft has discovered an alien world that might just support life as we know it. Here's what you need to know about Earth's new celestial cousin, Kepler-22b:

What exactly is the Kepler mission?The Kepler spacecraft, which launched in 2009, is studying part of our neighborhood in the Milky Way Galaxy to see if there are any Earth-size planets within their own solar system's "habitable zone," meaning the planet orbits its star at a distance that could create conditions suitable to host life as we know it. Kepler is constantly monitoring the brightness of more than 100,000 stars. Based on fluctuations in brightness, scientists here on Earth crunch the numbers to see if there are planets orbiting those stars, and if they are within the "habitable zone."

Why are scientists so excited about this new planet? It's the first planet confirmed by Kepler that could "conceivably harbor life," says Mike Wall at Space.com. That confirmation is key. Kepler has already found 2,326 "potential planets," which "would quadruple the current tally of worlds known beyond our solar system." Out of those potential planets, about 54 are in the habitable zone, and 68 are "roughly Earth-size." As scientists sift through heaps of data, Kepler-22b is the first to officially be confirmed.

And what makes Kepler-22b so special?The "Earth-like" planet is 2.4 times larger than Earth and orbits its star much as our planet orbits the sun. Kepler-22b's calendar year takes 290 days. The planet boasts a "balmy temperature" of 72 degrees, which "would support the existence of liquid water," says BBC News. Kepler-22b gets about 25 percent less sunlight than Earth.

Great! So when do we move there?Not so fast — Kepler-22b is 600 light years away from Earth. So, says Kara Swisher at All Things D, "if any geek is planning a star trek, it will take a lot of rocket fuel."